1. Field of the Invention
The present invention relates to a fuel supply apparatus for a vehicle, and more particularly to a fuel supply apparatus for a vehicle provided with a plurality of fuel supply systems to an internal combustion engine.
2. Description of the Background Art
As a configuration of an internal combustion engine, one having both an intake manifold injector for injecting fuel into an intake port and an in-cylinder injector for injecting fuel into a cylinder is known. In this internal combustion engine, fuel injection control is carried out by combining intake manifold injection using the intake manifold injector and in-cylinder direct injection using the in-cylinder injector in accordance with an operation state.
In such an internal combustion engine, the pressure of the fuel injected from the in-cylinder injector, which sprays the fuel directly into the cylinder, needs to be set to a high pressure. Meanwhile, the pressure of the fuel injected from the intake manifold injector is lower than the pressure required for the in-cylinder injector. As such, in a fuel supply apparatus for the internal combustion engine, a plurality of fuel supply systems different in pressure of the supply fuel are arranged.
In particular, in the configuration where a high-pressure fuel pump provided in a fuel supply system supplying fuel to the in-cylinder injector (i.e., high-pressure fuel supply system) discharges excess fuel back to the fuel intake side at every discharge stroke, it has been pointed out that pulsation in fuel pressure occurs in a fuel supply system supplying fuel to the intake manifold injector (i.e., low-pressure fuel supply system) (e.g., Japanese Patent Laying-Open No. 11-351043; hereinafter, referred to as “Patent Document 1”).
Patent Document 1 proposes a configuration for suppressing the influence of such pulsation in fuel pressure on the intake manifold injector (auxiliary fuel injection valve), wherein a fuel filter is arranged at a fuel pipe, between a fuel return port of a high-pressure regulator adjusting the fuel injection pressure of the in-cylinder injector (main fuel injection valve) and a connection port to a fuel supply pipe to the intake manifold injector (auxiliary fuel injection valve). In the fuel injection control apparatus disclosed in Patent Document 1, provision of the fuel filter can prevent the pulsation in fuel pressure, generated due to the returned excess fuel, from adversely affecting the fuel pressure of the intake manifold injector (auxiliary fuel injection valve).
A configuration for a fuel supply apparatus is also proposed (e.g., Japanese Patent Laying-Open No. 08-082250; hereinafter, referred to as “Patent Document 2”), wherein a fuel supply cutoff valve is arranged at a fuel pipe so as to prevent leakage of fuel when an engine is damaged due to collision of the vehicle or the like. In the fuel leakage preventing apparatus disclosed in Patent Document 2, the fuel supply cutoff valve is closed when an acceleration sensor detects a change in acceleration exceeding a prescribed value.